The present invention relates to a scroll fluid machine such as a scroll vacuum pump or a scroll compressor.
A scroll fluid machine comprises a fixed scroll and an orbiting scroll which engages with the fixed scroll to form a compression chamber. The orbiting scroll revolves with an eccentric axial portion of a driving shaft connected to a driving source, so that the compression chamber decreases in volume toward the center, thereby compressing fluid.
Between the fixed scroll and orbiting scroll, a self-rotation-preventing device is interposed to prevent the orbiting scroll from rotating on its own axis when the driving shaft rotates. JP2003-202030A discloses that a self-rotation-preventing device is supported by elastic materials such as an O-ring made of fluororubber in a support hole of the orbiting scroll.
However, such a scroll fluid machine is used in a chemically-attacking gas and the O-ring deteriorates for a short time not only to make impossible for the O-ring to adjust an error in orbiting motion but also to loosen engagement of the scrolls, so that smooth motion is not achieved. It is not preferable to use elastic material such as fluororubber under such severe condition.